Bowlers strike with a hot hand, too

By Helen Dodson

January 12, 2012

Is the so-called “hot hand” phenomenon in sports a reality or just an illusion based on misperception of random sequences? For the second time in recent months, a Yale study supports the notion that it is real. The study appears online in the journal PLoS One.

The “hot hand” phenomenon refers to the belief that an athlete is more likely to make successful shots if the previous shots were successful. But until recently, there was no scientific evidence to support the existence of this phenomenon.

Last October, Gur Yaari, computational biologist at Yale School of Medicine, and colleague Shmuel Eisenmann demonstrated the existence of the phenomenon in basketball. They showed that there was a significant increase in basketball players’ chances of hitting the second free throw in a two-shot series compared to the first one, and that the probability of hitting the second shot is greater following a hit than a miss. It was unclear, however, whether there was a cause and effect (causal) connection between the result of one shot and the next.

In a new study, Yaari and colleague Gil David of the Yale Department of Mathematics showed that the “hot hand” phenomenon exists among bowlers as well. They also found evidence that the phenomenon is not due to a causal feedback mechanism, commonly referred to as “success breeds success,” but is a consequence of large fluctuations in player performances over time that result in some bad games and some very good games.

The researchers analyzed large amounts of data from the Professional Bowling Association, studying the results from available records of the top 100 players.

The performances of individual players fluctuated significantly. Researchers noted that within each game successes (strikes) and failures (non-strikes) were not necessarily clustered together, but spread out uniformly.

They found that although the result of one frame does not directly influence the next (a strike does not “cause” another strike and a miss does not “cause” another miss), it was clear that getting strikes in one game made it more likely that a player would get more strikes in that game – hence the presence of the “hot hand” phenomenon.

Researchers showed that such correlations in good and bad games can be used to improve the prediction power of the last frames in a game based on the scores in the beginning.

“The observed correlation allows us to improve our ability to predict the result of the last frames of a game based on the series of preceding frames,” Yaari explained. “The fact that a player had good results in the first eight frames of a game indicates that the probability of bowling a strike in the last two frames will be higher.”

So what causes the “hot hand” phenomenon? The Yale team said there is more research to be done.

“Our study shows that a player's performance is not affected by the results of previous trials, but rather by other factors,” Yaari said. “It shows that in contrast to previous belief, athlete's results could not be explained by pure random independent process. This opens the door for future studies addressing the question of what really cause athletes to perform better and how could they use this kind of knowledge to improve their performance.”